Most people who are comfortable buying a ribeye at the meat counter freeze up at the fish counter. They do not know what is good, what is fresh, what is sustainable, or what they are even looking at. And unlike a steak that is tolerant of being a day or two old, seafood is unforgiving — the difference between today's catch and three-day-old fish is the difference between a great dinner and a trip to the bathroom.
Direct Answer
Fresh seafood should smell like the ocean or a clean lake — briny, slightly sweet, not fishy. If it smells fishy, it is old. Whole fish should have clear, bright eyes (cloudy = old), firm flesh that springs back when pressed (mushy = old), and bright red gills (brown or gray = old). Fillets should be moist and glossy with no browning at the edges. Shrimp should smell neutral, not of ammonia. Always ask the counterperson three questions: when did this come in, is it fresh or previously frozen, and where was it caught (or farmed)?
How to Assess Freshness at the Counter
Your nose is your best tool. Fresh fish barely smells at all — a mild, clean, oceanic scent. The ammonia and fishiness that most people associate with seafood is the smell of decomposition. Trimethylamine (TMA) is the compound responsible for that fishy odor, and it is produced by bacteria breaking down the amino acid trimethylamine oxide (TMAO) that is naturally present in fish tissue. The more TMA, the older the fish. If you can smell it from two feet away, walk past it.
For whole fish: the eyes should be clear, bright, and slightly bulging — not sunken or cloudy. The gills should be bright red or deep pink — not brown, gray, or slimy. The skin should be shiny with tight-fitting scales (loose scales indicate rough handling or age). The flesh should be firm — press it with a finger and it should spring back. If the indentation stays, the muscle fibers have broken down from aging.
For fillets: the flesh should look moist and translucent, not dried out or opaque at the edges. There should be no gaps between the muscle layers (called gaping — indicates the fish was not handled properly or is too old). The color should be consistent — browning at the edges of salmon, yellowing on white fish, or dark spots on any species are age indicators. A thin layer of clear liquid on the surface is normal. Thick, milky liquid is not.
For shrimp: they should smell neutral or slightly briny. Any ammonia smell is a hard no. The shells should be firm and intact, with no black spots (melanosis — enzyme-driven darkening that indicates age). Fresh shrimp have a slightly translucent appearance. Fully opaque shrimp are either cooked or old.
Previously Frozen vs Fresh: The Secret Most Fish Counters Don't Volunteer
Here is a fact that changes how you shop for seafood: the majority of fish at the fish counter was previously frozen and thawed for display. This is not a scam — it is logistics. Most wild-caught fish is flash-frozen on the boat or at the processing facility within hours of harvest. Flash-freezing at -40°F preserves quality remarkably well. The previously frozen fish sitting on ice at the counter may actually be higher quality than fresh fish that was not frozen but took 5 days to get from the dock to your store.
The problem arises when the counter does not disclose this. If you buy previously frozen fish from the counter and refreeze it at home, the quality degrades significantly — double freezing damages cell structure and produces mushy texture. Ask the counterperson: is this fresh or previously frozen? If it was previously frozen, plan to use it within 1-2 days and do not refreeze.
The practical takeaway: for species that are commonly frozen at sea (most shrimp, most wild salmon, most tuna, most cod), buying from the frozen aisle and thawing yourself is often a better choice than buying the thawed version from the counter. You control the thaw timing, you know the freeze history, and it is usually cheaper. ButcherIQ includes a seafood freshness guide that helps you identify species, assess quality, and make the fresh-vs-frozen decision at the counter.
Sustainability: Making Responsible Choices Without a PhD
Overfishing is a real and serious problem, but the individual consumer does not need to memorize which species are endangered. Two shortcuts that cover 90% of sustainable seafood shopping:
First, look for certification labels. The MSC (Marine Stewardship Council) blue fish label on wild-caught seafood and the ASC (Aquaculture Stewardship Council) green label on farmed seafood indicate third-party verified sustainable practices. These certifications are not perfect, but they are meaningful — the standards are rigorous enough that many fisheries and farms cannot meet them.
Second, use the Monterey Bay Aquarium Seafood Watch program (available as an app and a website). It categorizes species by region into Best Choices, Good Alternatives, and Avoid. A 10-second search tells you whether the Atlantic salmon at the counter is responsibly farmed or not. The recommendations are updated regularly as fishery conditions change.
General guidelines: farmed shellfish (mussels, oysters, clams) are almost universally sustainable — they require no feed and actually improve water quality. Wild Alaska salmon is well-managed. Atlantic cod has recovered from historic overfishing and is increasingly sustainable from well-managed fisheries. Avoid: shark, bluefin tuna, imported shrimp without certification (often from farms with poor environmental practices), and orange roughy (extremely slow-growing deep-sea fish that cannot sustain commercial fishing pressure).